The present invention relates to a contour compensating circuit for compensating for the contour of a two-dimensional image formed by a video signal.
There is known a contour compensating circuit as shown in FIG. 1A for clarifying the contour of a two-dimensional image displayed through the process of reproducing a video signal. The contour compensating circuit includes a secondary differentiating circuit 1 for obtaining a secondary differentiated signal from the video signal, a delay adjusting circuit 2 for relatively compensating for the delay of the secondary differentiated signal by delaying the video signal, and a subtraction circuit 3 for synthesizing the outputs of these circuits.
Referring to FIG. 1A, the operational principle of such a circuit will be described. A primary differentiated signal is obtained by differentiating a input video signal having a waveform as shown in FIG. 1B. The primary differentiated signal is further differentiated to obtain a secondary differentiated signal. The secondary differentiated signal is superposed on the input video signal to cause pre and post overshooting in the contour portion of the video signal so as to obtain an output video signal whose level difference and signal level changes are boosted. When the output video signal is reproduced by a display device (not shown), the contour portion of the image is stressed.
The contour portions of the displayed image formed are thus stressed. However, the stronger the contour is stressed, the larger they are of the stressed contour portion becomes. There is thus a drawback in that the contour of the image may be stressed excessively.